Biology Chapter: Metabolism and Energy

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary goal of photosynthesis?

To convert carbon dioxide into glucose (correct)

To generate high-energy electrons

To store energy as glucose

To produce oxygen from water

Where do the light-dependent reactions of photosynthesis occur?

In the stroma

In the cytoplasm

In the thylakoids (correct)

In the mitochondria

Which of the following molecules is NOT produced during the light-dependent reactions?

NADPH

ATP

Glucose (correct)

Oxygen

How many turns of the Calvin Cycle are required to synthesize one molecule of glucose?

6 turns Signup and view all the answers

What is produced by the oxidation of water in the light-dependent reactions?

Oxygen Signup and view all the answers

What enzyme is responsible for capturing carbon dioxide during the Calvin Cycle?

RUBISCO Signup and view all the answers

Which of the following statements is true regarding lactic acid fermentation?

It produces lactic acid as a byproduct Signup and view all the answers

What is one of the main functions of cell division in multicellular organisms?

To form gametes for reproduction Signup and view all the answers

What is the primary function of catabolism in metabolism?

To break down macromolecules, releasing energy. Signup and view all the answers

Which statement best describes potential energy?

Stored energy that can exist in various forms like mechanical or nuclear. Signup and view all the answers

According to the First Law of Thermodynamics, which of the following is true?

Energy can only be transformed or transferred. Signup and view all the answers

What does a negative change in Gibbs Free Energy (ΔG) indicate for a reaction?

The reaction is spontaneous and does not need outside energy. Signup and view all the answers

What role does ATP play in cellular processes?

It functions as the primary energy currency of the cell. Signup and view all the answers

Which of the following accurately describes activation energy?

It is the initial energy required to start a reaction. Signup and view all the answers

What is the effect of enzymes on chemical reactions?

They lower the activation energy, speeding up the reaction. Signup and view all the answers

Which example shows an endergonic reaction?

Photosynthesis converting sunlight into glucose. Signup and view all the answers

Which cyclins are specifically known to activate CDKs at different stages of the cell cycle?

Cell cycle cyclins Signup and view all the answers

What is the primary function of the protein p53 in the cell cycle?

To initiate apoptosis during DNA damage Signup and view all the answers

What happens when tumor suppressor genes lose their function?

Uncontrolled cell growth occurs Signup and view all the answers

How do proto-oncogenes contribute to the cell cycle?

By driving the cell cycle forward Signup and view all the answers

What is the primary mechanism of bacterial reproduction?

Binary Fission Signup and view all the answers

What defines a diploid cell?

A cell with two copies of each chromosome Signup and view all the answers

What is the role of plasmids in bacteria?

They replicate independently of the bacterial chromosome Signup and view all the answers

During which phase does p53 halt the cell cycle when DNA damage is detected?

G1 phase Signup and view all the answers

What is the primary function of histone proteins in eukaryotic cells?

To package DNA into chromatin Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

S phase Signup and view all the answers

Which checkpoint determines if conditions are favorable for cell division to proceed?

G1 Checkpoint Signup and view all the answers

What role do cyclins and CDKs play in the cell cycle?

They promote cell cycle progression as positive regulators. Signup and view all the answers

Which phase of mitosis is characterized by the alignment of chromosomes at the metaphase plate?

Metaphase Signup and view all the answers

What occurs during cytokinesis in animal cells?

A cleavage furrow forms and the cell splits Signup and view all the answers

What effect does the binding of external signals, such as growth factors, have on the cell cycle?

It can potentially trigger internal reactions that influence cell division. Signup and view all the answers

Which statement best describes the internal control system regulating the cell cycle?

It involves both positive and negative regulators. Signup and view all the answers

What event occurs during Prophase I of meiosis that is not present in mitosis?

Pairing of homologous chromosomes Signup and view all the answers

What is the outcome of Meiosis II?

Four genetically different haploid cells are generated Signup and view all the answers

Which mechanism contributes to genetic variability during sexual reproduction by separating homologous chromosomes?

Independent assortment Signup and view all the answers

During which stage of meiosis do homologous chromosomes segregate to opposite poles of the cell?

Anaphase I Signup and view all the answers

What occurs during crossing over in Prophase I?

Homologous chromosomes exchange DNA segments. Signup and view all the answers

What does meiosis ultimately restore after fertilization?

Diploidy Signup and view all the answers

What is a consequence of random joining of male and female gametes during fertilization?

Increase in genetic variability Signup and view all the answers

Which meiotic phase involves tetrads aligning at the metaphase plate?

Metaphase I Signup and view all the answers

Study Notes

Metabolism

The sum of all biochemical reactions within a cell, essential for energy production and sustaining life.
Catabolism involves breaking down macromolecules into simpler components, releasing energy.
Anabolism involves building complex molecules from simpler ones using energy released from catabolism.

Energy

The capacity to do work or cause change.
Potential energy: stored energy, including chemical, mechanical, gravitational, and nuclear.
Kinetic energy: energy of motion, including water waves, electricity, muscle contraction, and vesicle movement.

Thermodynamics

First Law of Thermodynamics: energy is conserved; it cannot be created or destroyed, only transformed or transferred.
Second Law of Thermodynamics: energy transfers are inefficient; some energy is lost as heat or reduced organization, leading to increased entropy (disorder).
Gibbs Free Energy (G): usable energy available to do work.
ΔG: Change in free energy; calculated as ΔG = ΔH - TΔS where:
- T = absolute temperature in Kelvin
- H = change in enthalpy (potential energy)
- S = change in entropy
Exergonic Reactions: ΔG < 0; spontaneous, no external energy required.
Endergonic Reactions: ΔG > 0; non-spontaneous, requiring external energy input.

Adenosine Triphosphate (ATP)

The energy currency of the cell.
Hydrolysis of ATP is a spontaneous reaction releasing significant free energy.
Powers cellular reactions with a positive ΔG (coupling).

Activation Energy

The initial energy required to start a reaction.

Enzymes

Biological catalysts that lower activation energy, increasing the rate of reaction.
Remain unchanged after the reaction.
Cannot alter the Gibbs free energy of a reaction.

Photosynthesis

A non-spontaneous reaction requiring energy from sunlight.
Goal: Reduce carbon dioxide to glucose.

Location and Process of Photosynthesis

Occurs in chloroplasts of plants.
Divided into two parts: Light-Dependent Reactions and Light-Independent Reactions.

Light-Dependent Reactions (Light Cycle)

Occur in the thylakoids of chloroplasts.
Light Absorption: Pigments like chlorophyll absorb sunlight, leading to charge separation and production of high-energy electrons.
Electron Transfer: High-energy electrons travel through an electron-transfer protein system in the thylakoid membrane, generating a proton gradient and ultimately reducing NADP+ to NADPH.
ATP Synthesis: The proton gradient (proton motive force) powers ATP synthesis via ATP synthase.
Water Oxidation: Water is split, releasing oxygen to replenish lost electrons from the charge separation reaction.
Key Molecules Produced: ATP, NADPH, and O2.

Light-Independent Reactions (Calvin Cycle, Dark Cycle)

Occur in the stroma of chloroplasts.
Carbon Dioxide Capture: Carbon dioxide is captured by ribulose 1,5-bisphosphate (5 carbon) via the RUBISCO enzyme.
Synthesis of Glyceraldehyde-3-Phosphate (C3): Two molecules of glyceraldehyde-3-phosphate, a key glycolysis intermediate, are synthesized using ATP and NADPH from the light cycle.
Glucose Synthesis: Six turns of the Calvin cycle are required to synthesize one molecule of glucose from six molecules of CO2.

Cell Division:

Three key functions:
- Development, growth, and repair of tissues in multicellular animals (Mitosis).
- Formation of gametes (eggs and sperm) for sexual reproduction in multicellular animals (Meiosis).
- Reproduction of an entire unicellular organism (e.g., bacteria).

Cell Division in Eukaryotes: Mitosis

Required tasks: Growth, copying genetic material, and physically splitting into two daughter cells.

Organization of DNA in Eukaryotic Cells

DNA forms a complex with proteins, called chromatin.
The fundamental unit of chromatin is the nucleosome, composed of DNA wrapped around a core of eight histone proteins.

The Cell Cycle

Interphase: G1 phase (growth), S phase (DNA replication and duplication), G2 phase (preparation for cell division).
Mitotic Phase: Prophase, Prometaphase, Metaphase, Anaphase, Telophase, and Cytokinesis.

Regulation of the Cell Cycle

Loss of control can lead to cancer.

External Controls

Primarily rely on surface receptors that bind signals like peptide hormones, growth factors, surface groups on other cells, or extracellular matrix molecules.
These signals can trigger internal reactions speeding, slowing, or stopping cell division.

Internal Controls

Monitor cell cycle progression through checkpoints to ensure proper completion of phases:
- G1 Checkpoint: Determines favorable conditions for cell division.
- G2 Checkpoint: Ensures chromosome replication and DNA integrity.
- M Checkpoint (end of metaphase): Ensures correct chromosome alignment.

Internal Control System: Positive and Negative Regulators

Positive Regulators: Promote cell cycle progression, including cyclins and cyclin-dependent kinases (CDKs).
- CDKs are activated by cyclins and phosphorylate target proteins, regulating their activities.
- Four classes of cyclins activate CDKs at specific cell cycle stages.
Negative Regulators: Halt the cell cycle, including pRB, p53, and p21.
- Known as tumor suppressors, as their dysfunction can lead to uncontrolled cell growth (cancer).
- p53 arrests the cell cycle in G1 phase upon detecting DNA damage until repair. It can also induce apoptosis if the damage cannot be repaired.
Conversion of Normal Cells to Cancer Cells:
- Occurs due to mutations in proto-oncogenes (drive cell cycle forward).
- Mutated proto-oncogenes become oncogenes.

Cell Division in Prokaryotes: Binary Fission

Similar to mitosis but with a different purpose.
- Mitosis in multicellular organisms leads to growth or cell replacement.
- Binary fission is how bacteria reproduce and increase their population.
The bacterial chromosome is a circular DNA molecule, packed into the nucleiod region of the cell.
Replication begins at the origin of replication of the chromosome, catalyzed by enzymes.
The two origins migrate to opposite ends of the cell.
Division of the cytoplasm occurs through the growth of a cell wall partition.

Sexual Reproduction

Occurs only in eukaryotes.
Requires fertilization: fusion of two haploid cells (gametes) to form a diploid zygote.
The zygote develops into an adult organism through mitosis.

Ploidy: The Number of Sets of Chromosomes in a Cell

Haploid (n): one copy of each chromosome.
Diploid (2n): two copies of each chromosome.

Generation of Haploid Cells (Gametes)

Meiosis: division of germ cells.
Two rounds of nuclear division (I and II) to reduce the chromosome number prior to fertilization, restoring diploidy.
DNA replicates during premeiotic interphase, producing sister chromatids for each chromosome.
Meiotic phases are similar to mitotic ones.

Meiosis I: First Cell Division

Key events not seen in mitosis:
- Prophase I: Homologous chromosomes pair, held together by the synaptonemal complex. Non-sister chromatids exchange DNA segments through crossing-over (chiasmata).
- Metaphase I: Tetrads (4 sister chromatids) align at the metaphase plate; homologous chromosomes orient towards opposite poles.
- Anaphase I: Homologous chromosomes segregate toward opposite poles, reducing the chromosome number to haploid.
- Telophase and Cytokinesis I: Two haploid daughter cells are formed, each chromosome still with two chromatids.

Meiosis II: Second Cell Division

Similar to mitotic division, but results in four haploid cells, each containing half the number of chromosomes.

Genetic Variability in Offspring

Why individuals don't look exactly alike, except for identical twins.
Sexual reproduction introduces genetic variability through:
- Crossing Over: Exchange of genetic material between homologous chromosomes during Prophase I.
- Independent Assortment: Random alignment of homologous chromosomes at the metaphase plate, resulting in random distribution of chromosomes in daughter cells.
- Random Joining: Random fusion of male and female gametes during fertilization.

Mitosis vs. Meiosis

Mitosis: Produces two identical daughter cells, each with the same number of chromosomes as the parent cell. Used for growth, repair, and asexual reproduction.
Meiosis: Produces four genetically different daughter cells, each with half the number of chromosomes as the parent cell. Used for sexual reproduction and genetic diversity.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the fundamental concepts of metabolism, energy types, and thermodynamics in cellular processes. Understand catabolism, anabolism, and how the laws of thermodynamics govern energy transformations. This quiz will test your knowledge on these essential biological principles.